FIG. 1 is a diagram for explaining a delay which is occurred when a downlink signal transmission is processed in LTE system.
As shown in FIG. 1, 1 TTI (Transmit Time Interval) has a length of 1 ms in LTE system. If an eNB transmits data to a UE, the data arrives at the UE after time as much as “A” is delayed. The time corresponds to propagation delay in wireless communication.
Having received the data, the UE requires time as much as B, C, D, E, and F for buffering the data, decoding a control channel, decoding the data, preparing a response signal, and transmitting the response signal prior to time corresponding to a trimming advanced.
In general, in LTE system, a delay of 4 ms corresponding to 4 TTI occurs until a confirmation response of a UE is received after data is transmitted from an eNB.